Technical Field
The present invention relates to a capacitive load driving circuit.
Related Art
One known inkjet printer for discharging ink to print an image or document uses piezoelectric elements (for example, piezo elements). The piezoelectric elements are provided so as to respectively correspond to a plurality of nozzles in a print head and each, by being driven in conformity with a control signal, causes a predetermined amount of ink to be discharged from the nozzles at a predetermined timing. The piezoelectric elements, when viewed electrically, are a capacitive load similar to a capacitor, and therefore a sufficient electrical current needs to be supplied in order to actuate the piezoelectric elements of each of the nozzles.
For this reason, a conventional configuration has been to amplify an original signal with an amplifier circuit and supply the amplified control signal to the print head to drive the piezoelectric elements. Amplifier circuits include a format where the original signal undergoes electrical current amplification with a class AB or the like (linear amplification; see Japanese laid-open patent publication 2009-190287), or a format where the original signal is modulated by pulse width modulation, pulse density modulation, or the like, and then demodulated with a low-pass filter (class D amplification; see Japanese laid-open patent publication 2010-114711), and so forth.
Beyond amplifying the original signal with an amplifier circuit, a format in which the voltage applied to the piezoelectric elements is switched at a plurality of stages (voltage switching format; see Japanese laid-open patent publication 2004-153411) has also been proposed.